The present invention relates to apparatus for extracting or adding measure volumes of liquid from or to flow lines or tanks.
Various manufacturing operations require that the immediate or overall composition of a liquid flowing through a pipe be monitored. Such monitoring ordinarily is accomplished with apparatus denoted as samplers, which take samples of liquid from a main body thereof. Where a composite sample of the liquid is required, the sampler may be operated to withdraw a series of small, measured amounts of the liquid as it passes a sampling point. The small, measured amounts are collected, and form a representative, composite sample of the total volume of liquid.
Other uses for samplers are in on-line analysis applications, in which the immediate composition of a liquid must be determined. For this application, the individual samples of liquid are not collected as a composite sample, but instead are analyzed separately.
To obtain samples, some samplers continuously divert streams of liquid from the flow lines or tanks, and from the diverted streams, the samples are removed in various ways. Attempts to withdraw small, measured quantities directly from the pipes or tanks, however, have presented many problems not altogether satisfactorily solved. For example, where liquid receiving holes or slots are extended directly into a pipe, the sampler often requires an orienting mechanism, and the sampled material can build up in such holes and slots and either block the same or contaminate subsequent samples. In addition, conventional samplers often are difficult to disassemble for inspection, cleaning and replacement of parts, and excessive leakage and clogging are problems common to many types of samplers.
Heretofore, samplers of the general type have been used to obtain samples of relatively nonviscous liquids. In recent years, a need has arisen to sample liquids which are viscous, for example catsup, mayonnaise, juice concentrate, toothpaste and heavy grease. Conventional samplers do not perform satisfactorily when used to sample such highly viscous liquids, since the sampled material is too thick to effectively flow into and then off and out of the sampler for collection. Two types of samplers adapted to handle relatively viscous materials are taught by Johnson et al U.S. Pat. No. 4,269,064, and by my U.S. Pat. No. 4,475,410, each of which defines a sample chamber between two members that may be moved together to collapse the chamber and eject the sample under positive pressure. However, each sampler is somewhat limited in versatility because of a lack of positive independent control over movement of the two members.
In addition to extracting measured samples of liquid, it often is necessary to meter measured volumes of liquid into lines or tanks. For such situations, it would be advantageous if the same apparatus used to extract samples could also be used as a metering pump to add measured volumes of liquid to the line or tank.